PangoContext

typedef struct _PangoContext PangoContext;

The PangoContext structure stores global information used to control the itemization process.

PangoItem

typedef struct {
  gint offset;
  gint length;
  gint num_chars;
  PangoAnalysis analysis;
} PangoItem;

The PangoItem structure stores information about a segment of text. It contains the following fields:

PangoAnalysis

typedef struct {
  PangoEngineShape *shape_engine;
  PangoEngineLang  *lang_engine;
  PangoFont *font;
  guint8 level;
  PangoLanguage *language;
  GSList *extra_attrs;
} PangoAnalysis;

The PangoAnalysis structure stores information about the properties of a segment of text. It has the following fields:

enum PangoDirection

typedef enum {
  PANGO_DIRECTION_LTR,
  PANGO_DIRECTION_RTL,
  PANGO_DIRECTION_TTB_LTR,
  PANGO_DIRECTION_TTB_RTL,
  PANGO_DIRECTION_WEAK_LTR,
  PANGO_DIRECTION_WEAK_RTL,
  PANGO_DIRECTION_NEUTRAL
} PangoDirection;

The PangoDirection type represents a direction in the Unicode bidirectional algorithm; not every value in this enumeration makes sense for every usage of PangoDirection; for example, the return value of pango_unichar_direction() and pango_find_base_dir() cannot be PANGO_DIRECTION_WEAK_LTR or PANGO_DIRECTION_WEAK_RTL, since every character is either neutral or has a strong direction; on the other hand PANGO_DIRECTION_NEUTRAL doesn't make sense to pass to pango_log2vis_get_embedding_levels().

The PANGO_DIRECTION_TTB_LTR, PANGO_DIRECTION_TTB_RTL values come from an earlier interpretation of this enumeration as the writing direction of a block of text and are no longer used; See the Text module of the CSS3 spec for how vertical text is planned to be handled in a future version of Pango. The explanation of why PANGO_DIRECTION_TTB_LTR is treated as PANGO_DIRECTION_RTL can be found there as well.

PANGO_TYPE_DIRECTION

#define PANGO_TYPE_DIRECTION (pango_direction_get_type())

The GObject type for PangoDirection.

pango_itemize ()

GList*      pango_itemize                   (PangoContext *context,
                                             const char *text,
                                             int start_index,
                                             int length,
                                             PangoAttrList *attrs,
                                             PangoAttrIterator *cached_iter);

Breaks a piece of text into segments with consistent directional level and shaping engine. Each byte of text will be contained in exactly one of the items in the returned list; the generated list of items will be in logical order (the start offsets of the items are ascending).

cached_iter should be an iterator over attrs currently positioned at a range before or containing start_index; cached_iter will be advanced to the range covering the position just after start_index + length. (i.e. if itemizing in a loop, just keep passing in the same cached_iter).

pango_itemize_with_base_dir ()

GList*      pango_itemize_with_base_dir     (PangoContext *context,
                                             PangoDirection base_dir,
                                             const char *text,
                                             int start_index,
                                             int length,
                                             PangoAttrList *attrs,
                                             PangoAttrIterator *cached_iter);

Like pango_itemize(), but the base direction to use when computing bidirectional levels (see pango_context_set_base_dir()), is specified explicitely rather than gotten from the PangoContext.

pango_item_free ()

void        pango_item_free                 (PangoItem *item);

Free a PangoItem and all associated memory.

pango_item_copy ()

PangoItem*  pango_item_copy                 (PangoItem *item);

Copy an existing PangoItem structure.

pango_item_new ()

PangoItem*  pango_item_new                  (void);

Creates a new PangoItem structure initialized to default values.

pango_item_split ()

PangoItem*  pango_item_split                (PangoItem *orig,
                                             int split_index,
                                             int split_offset);

Modifies orig to cover only the text after split_index, and returns a new item that covers the text before split_index that used to be in orig. You can think of split_index as the length of the returned item. split_index may not be 0, and it may not be greater than or equal to the length of orig (that is, there must be at least one byte assigned to each item, you can't create a zero-length item). split_offset is the length of the first item in chars, and must be provided because the text used to generate the item isn't available, so pango_item_split() can't count the char length of the split items itself.

pango_reorder_items ()

GList*      pango_reorder_items             (GList *logical_items);

From a list of items in logical order and the associated directional levels, produce a list in visual order. The original list is unmodified.

pango_context_new ()

PangoContext* pango_context_new             (void);

Creates a new PangoContext initialized to default value.

This function is only useful when implementing a new backend for Pango, something applications won't do. You should use the context creation function for the backend you are using, for example, pango_xft_get_context(), pango_win32_get_context() or, pango_ft2_font_map_create_context().

If you are using Pango as part of a higher-level system, that system may have it's own ways of create a PangoContext. For instance, the GTK+ toolkit has, among others, gdk_pango_context_get_for_screen(), and gtk_widget_get_pango_context().

pango_context_set_font_map ()

void        pango_context_set_font_map      (PangoContext *context,
                                             PangoFontMap *font_map);

Sets the font map to be searched when fonts are looked-up in this context. This is only for internal use by Pango backends, a PangoContext obtained via one of the recommended methods should already have a suitable font map.

pango_context_get_font_map ()

PangoFontMap* pango_context_get_font_map    (PangoContext *context);

Gets the PangoFontmap used to look up fonts for this context.

Since 1.6

pango_context_get_font_description ()

PangoFontDescription* pango_context_get_font_description
                                            (PangoContext *context);

Retrieve the default font description for the context.

pango_context_set_font_description ()

void        pango_context_set_font_description
                                            (PangoContext *context,
                                             const PangoFontDescription *desc);

Set the default font description for the context

pango_context_get_language ()

PangoLanguage* pango_context_get_language   (PangoContext *context);

Retrieves the global language tag for the context.

pango_context_set_language ()

void        pango_context_set_language      (PangoContext *context,
                                             PangoLanguage *language);

Sets the global language tag for the context.

pango_context_get_base_dir ()

PangoDirection pango_context_get_base_dir   (PangoContext *context);

Retrieves the base direction for the context. See pango_context_set_base_dir().

pango_context_set_base_dir ()

void        pango_context_set_base_dir      (PangoContext *context,
                                             PangoDirection direction);

Sets the base direction for the context.

The base direction is used in applying the Unicode bidirectional algorithm; if the direction is PANGO_DIRECTION_LTR or PANGO_DIRECTION_RTL, then the value will be used as the paragraph direction in the Unicode bidirectional algorithm. A value of PANGO_DIRECTION_WEAK_LTR or PANGO_DIRECTION_WEAK_RTL is used only for paragraphs that do not contain any strong characters themselves.

pango_context_get_matrix ()

const PangoMatrix* pango_context_get_matrix (PangoContext *context);

Gets the transformation matrix that will be applied when rendering with this context. See pango_context_set_matrix().

Since 1.6

pango_context_set_matrix ()

void        pango_context_set_matrix        (PangoContext *context,
                                             const PangoMatrix *matrix);

Sets the transformation matrix that will be applied when rendering with this context. Note that reported metrics are in the user space coordinates before the application of the matrix, not device-space coordiantes after the application of the matrix. So, they don't scale with the matrix, though they may change slightly for different matrices, depending on how the text is fit to the pixel grid.

Since 1.6

pango_context_load_font ()

PangoFont*  pango_context_load_font         (PangoContext *context,
                                             const PangoFontDescription *desc);

Loads the font in one of the fontmaps in the context that is the closest match for desc.

pango_context_load_fontset ()

PangoFontset* pango_context_load_fontset    (PangoContext *context,
                                             const PangoFontDescription *desc,
                                             PangoLanguage *language);

Load a set of fonts in the context that can be used to render a font matching desc.

pango_context_get_metrics ()

PangoFontMetrics* pango_context_get_metrics (PangoContext *context,
                                             const PangoFontDescription *desc,
                                             PangoLanguage *language);

Get overall metric information for a font particular font description. Since the metrics may be substantially different for different scripts, a language tag can be provided to indicate that the metrics should be retrieved that correspond to the script(s) used by that language.

The PangoFontDescription is interpreted in the same way as by pango_itemize(), and the family name may be a comma separated list of figures. If characters from multiple of these families would be used to render the string, then the returned fonts would be a composite of the metrics for the fonts loaded for the individual families.

pango_context_list_families ()

void        pango_context_list_families     (PangoContext *context,
                                             PangoFontFamily ***families,
                                             int *n_families);

List all families for a context.

pango_get_mirror_char ()

gboolean    pango_get_mirror_char           (gunichar ch,
                                             gunichar *mirrored_ch);

If ch has the Unicode mirrored property and there is another unicode character that typically has a glyph that is the mirror image of ch's glyph, puts that character in the address pointed to by mirrored_ch.

Use g_unichar_get_mirror_char() instead; the docs for that function provide full details.

pango_unichar_direction ()

PangoDirection pango_unichar_direction      (gunichar ch);

Determines the direction of a character; either PANGO_DIRECTION_LTR, PANGO_DIRECTION_LTR, or PANGO_DIRECTION_NEUTRAL.

pango_find_base_dir ()

PangoDirection pango_find_base_dir          (const gchar *text,
                                             gint length);

Searches a string the first character that has a strong direction, according to the Unicode bidirectional algorithm.

pango_break ()

void        pango_break                     (const gchar *text,
                                             int length,
                                             PangoAnalysis *analysis,
                                             PangoLogAttr *attrs,
                                             int attrs_len);

Determines possible line, word, and character breaks for a string of Unicode text.

pango_get_log_attrs ()

void        pango_get_log_attrs             (const char *text,
                                             int length,
                                             int level,
                                             PangoLanguage *language,
                                             PangoLogAttr *log_attrs,
                                             int attrs_len);

Computes a PangoLogAttr for each character in text. The log_attrs array must have one PangoLogAttr for each position in text; if text contains N characters, it has N+1 positions, including the last position at the end of the text. text should be an entire paragraph; logical attributes can't be computed without context (for example you need to see spaces on either side of a word to know the word is a word).

pango_find_paragraph_boundary ()

void        pango_find_paragraph_boundary   (const gchar *text,
                                             gint length,
                                             gint *paragraph_delimiter_index,
                                             gint *next_paragraph_start);

Locates a paragraph boundary in text. A boundary is caused by delimiter characters, such as a newline, carriage return, carriage return-newline pair, or Unicode paragraph separator character. The index of the run of delimiters is returned in paragraph_delimiter_index. The index of the start of the paragraph (index after all delimiters) is stored in next_paragraph_start.

If no delimiters are found, both paragraph_delimiter_index and next_paragraph_start are filled with the length of text (an index one off the end).

pango_default_break ()

void        pango_default_break             (const gchar *text,
                                             int length,
                                             PangoAnalysis *analysis,
                                             PangoLogAttr *attrs,
                                             int attrs_len);

This is the default break algorithm, used if no language engine overrides it. Normally you should use pango_break() instead; this function is mostly useful for chaining up from a language engine override. Unlike pango_break(), analysis can be NULL, but only do that if you know what you're doing. (If you need an analysis to pass to pango_break(), you need to pango_itemize() or use pango_get_log_attrs().)

PangoLogAttr

typedef struct {
  guint is_line_break : 1;      /* Can break line in front of character */

  guint is_mandatory_break : 1; /* Must break line in front of character */

  guint is_char_break : 1;      /* Can break here when doing char wrap */
  
  guint is_white : 1;           /* Whitespace character */

  /* cursor can appear in front of character (i.e. this is a grapheme
   * boundary, or the first character in the text)
   */
  guint is_cursor_position : 1;
  
  /* Note that in degenerate cases, you could have both start/end set on
   * some text, most likely for sentences (e.g. no space after a period, so
   * the next sentence starts right away)
   */
  
  guint is_word_start : 1;      /* first character in a word */
  guint is_word_end   : 1;      /* is first non-word char after a word */

  /* There are two ways to divide sentences. The first assigns all
   * intersentence whitespace/control/format chars to some sentence,
   * so all chars are in some sentence; is_sentence_boundary denotes
   * the boundaries there. The second way doesn't assign
   * between-sentence spaces, etc. to any sentence, so
   * is_sentence_start/is_sentence_end mark the boundaries of those
   * sentences.
   */
  guint is_sentence_boundary : 1;
  guint is_sentence_start : 1;  /* first character in a sentence */
  guint is_sentence_end : 1;    /* first non-sentence char after a sentence */

  /* if set, backspace deletes one character rather than
   * the entire grapheme cluster  
   */
  guint backspace_deletes_character : 1; 
} PangoLogAttr;

The PangoLogAttr structure stores information about the attributes of a single character.

pango_shape ()

void        pango_shape                     (const gchar *text,
                                             gint length,
                                             PangoAnalysis *analysis,
                                             PangoGlyphString *glyphs);

Given a segment of text and the corresponding PangoAnalysis structure returned from pango_itemize(), convert the characters into glyphs. You may also pass in only a substring of the item from pango_itemize().